Exemplary embodiments pertain to the art of analog to digital data transfer systems, specifically to a system to acquire analog to digital data using N2HET and HTU.
External Analog to Digital Converters (ADCs) are used due to several advantages over internal ADCs such as higher conversion speed, higher resolution, improved accuracy, etc. As the speed of ADCs increase, the faster the interface (from microcontroller side) must trigger, convert data, detect changes in the signal, etc. These system requirements are often felt in demanding applications like motor control. The traditional way of acquiring samples from external ADCs include using a serial peripheral interface (SPI) bus and external memory interface (EMIF). Since SPI is a serial transfer method, it can be slow. This speed reduction can be made worse because the SPI clock is limited to certain speed on most of the microcontrollers (around 20 MHz). Although EMIF is a parallel interface, it may not be suited to interface with all ADCs. The only way to use EMIF is through DMA to save CPU time for other critical tasks. DMA bandwidth for EMIF may become limited for following reasons.
Micro Controllers using Direct Memory Access (DMA) peripheral can face a bottleneck in systems with demanding applications like continuous excitation. For example, some applications require up to six channels of DMA at a rate of 10 KHz per channel. Further, DMA may be needed by several peripherals like SCI, I2C, etc for their data transfer needs. Using the central processing unit (CPU) for such tasks can result in undue system interruptions, which can also introduce system unreliability.